With Sejong I focus on popping as many GPs as I can with multiple popping and settling them,, plus going for the Freedom finisher ASAP and building everything with a specialist slot. I manage to grab the Statue of Lib at around 1600 AD, and then every city fills every specialist slot for the rest of the game for godly science, happiness and production.
With Babylon I used to bulb bulb bulb, and then firaxis kept going nerf nerf nerf, so I gave up on playing them for a long time. Korea, Inca and Ramesses were my top 3 favorites, and Im sure that Maya are going to become one of my favorites too now.
Sejongs +2 science per specialist and GP tile improvement is just awesome though, and now Great Scientists are nerfed hugely to only give the average of your last 6 turns worth of research for a bulb, making me think that settling them is always going to be better.